//
//  UIImage+ProportionalFill.m
//
//  Created by Matt Gemmell on 20/08/2008.
//  Copyright 2008 Instinctive Code.
//

#import "UIImage+ProportionalFill.h"

@implementation UIImage (MGProportionalFill)

- (UIImage*)imageToFitSize:(CGSize)fitSize method:(MGImageResizingMethod)resizeMethod
{
    float imageScaleFactor = 1.0;
#if __IPHONE_OS_VERSION_MAX_ALLOWED >= __IPHONE_4_0
    if ([self respondsToSelector:@selector(scale)]) {
        imageScaleFactor = [self scale];
    }
#endif

    float sourceWidth = [self size].width * imageScaleFactor;
    float sourceHeight = [self size].height * imageScaleFactor;
    float targetWidth = fitSize.width;
    float targetHeight = fitSize.height;
    BOOL cropping = !(resizeMethod == MGImageResizeScale);

    // Calculate aspect ratios
    float sourceRatio = sourceWidth / sourceHeight;
    float targetRatio = targetWidth / targetHeight;

    // Determine what side of the source image to use for proportional scaling
    BOOL scaleWidth = (sourceRatio <= targetRatio);
    // Deal with the case of just scaling proportionally to fit, without cropping
    scaleWidth = (cropping) ? scaleWidth : !scaleWidth;

    // Proportionally scale source image
    float scalingFactor, scaledWidth, scaledHeight;
    if (scaleWidth) {
        scalingFactor = 1.0 / sourceRatio;
        scaledWidth = targetWidth;
        scaledHeight = round(targetWidth * scalingFactor);
    }
    else {
        scalingFactor = sourceRatio;
        scaledWidth = round(targetHeight * scalingFactor);
        scaledHeight = targetHeight;
    }
    float scaleFactor = scaledHeight / sourceHeight;

    // Calculate compositing rectangles
    CGRect sourceRect, destRect;
    if (cropping) {
        destRect = CGRectMake(0, 0, targetWidth, targetHeight);
        float destX = 0.0, destY = 0.0;
        if (resizeMethod == MGImageResizeCrop) {
            // Crop center
            destX = round((scaledWidth - targetWidth) / 2.0);
            destY = round((scaledHeight - targetHeight) / 2.0);
        }
        else if (resizeMethod == MGImageResizeCropStart) {
            // Crop top or left (prefer top)
            if (scaleWidth) {
                // Crop top
                destX = 0.0;
                destY = 0.0;
            }
            else {
                // Crop left
                destX = 0.0;
                destY = round((scaledHeight - targetHeight) / 2.0);
            }
        }
        else if (resizeMethod == MGImageResizeCropEnd) {
            // Crop bottom or right
            if (scaleWidth) {
                // Crop bottom
                destX = round((scaledWidth - targetWidth) / 2.0);
                destY = round(scaledHeight - targetHeight);
            }
            else {
                // Crop right
                destX = round(scaledWidth - targetWidth);
                destY = round((scaledHeight - targetHeight) / 2.0);
            }
        }
        sourceRect = CGRectMake(destX / scaleFactor, destY / scaleFactor,
            targetWidth / scaleFactor, targetHeight / scaleFactor);
    }
    else {
        sourceRect = CGRectMake(0, 0, sourceWidth, sourceHeight);
        destRect = CGRectMake(0, 0, scaledWidth, scaledHeight);
    }

    // Create appropriately modified image.
    UIImage* image = nil;

#if __IPHONE_OS_VERSION_MAX_ALLOWED >= __IPHONE_4_0
    CGImageRef sourceImg = nil;
    if ([UIScreen instancesRespondToSelector:@selector(scale)]) {
        UIGraphicsBeginImageContextWithOptions(destRect.size, NO, 0.f); // 0.f for scale means "scale for device's main screen".
        sourceImg = CGImageCreateWithImageInRect([self CGImage], sourceRect); // cropping happens here.
        image = [UIImage imageWithCGImage:sourceImg scale:0.0 orientation:self.imageOrientation]; // create cropped UIImage.
    }
    else {
        UIGraphicsBeginImageContext(destRect.size);
        sourceImg = CGImageCreateWithImageInRect([self CGImage], sourceRect); // cropping happens here.
        image = [UIImage imageWithCGImage:sourceImg]; // create cropped UIImage.
    }

    CGImageRelease(sourceImg);
    [image drawInRect:destRect]; // the actual scaling happens here, and orientation is taken care of automatically.
    image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
#endif

    if (!image) {
        // Try older method.
        CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
        CGContextRef context = CGBitmapContextCreate(NULL, scaledWidth, scaledHeight, 8, (scaledWidth * 4),
            colorSpace, 1);
        CGImageRef sourceImg = CGImageCreateWithImageInRect([self CGImage], sourceRect);
        CGContextDrawImage(context, destRect, sourceImg);
        CGImageRelease(sourceImg);
        CGImageRef finalImage = CGBitmapContextCreateImage(context);
        CGContextRelease(context);
        CGColorSpaceRelease(colorSpace);
        image = [UIImage imageWithCGImage:finalImage];
        CGImageRelease(finalImage);
    }

    return image;
}

- (UIImage*)imageCroppedToFitSize:(CGSize)fitSize
{
    return [self imageToFitSize:fitSize method:MGImageResizeCrop];
}

- (UIImage*)imageScaledToFitSize:(CGSize)fitSize
{
    return [self imageToFitSize:fitSize method:MGImageResizeScale];
}

- (UIImage*)scaleToSize:(CGSize)size
{
    // 创建一个bitmap的context
    // 并把它设置成为当前正在使用的context
    UIGraphicsBeginImageContext(size);
    // 绘制改变大小的图片
    [self drawInRect:CGRectMake(0, 0, size.width, size.height)];
    // 从当前context中创建一个改变大小后的图片
    UIImage* scaledImage = UIGraphicsGetImageFromCurrentImageContext();
    // 使当前的context出堆栈
    UIGraphicsEndImageContext();
    // 返回新的改变大小后的图片
    return scaledImage;
}

@end
